The present invention relates to a novel ink jet recording method employing an actinic radiation curable ink.
Heretofore, widely employed as ink jet recording ink has been aqueous liquid ink (water based ink). Further, a hot-melt type ink jet recording method is proposed in which a hot-melt type ink comprising wax as a component, which is solid at room temperature, is used and the aforesaid ink is liquefied by heating and the like, ejected by application of any appropriate form of energy, deposited onto recording media, and cooled to a solid to form recording dots.
Since the aforesaid ink is solid at room temperature, no staining occurs during handling. Further, since it is possible to minimize the evaporation amount of the aforesaid ink during melting, no clogging occurs. In addition, since the aforesaid ink is immediately solidified after deposition onto recording media, no “bleeding” occurs. As a result, the aforesaid ink exhibits advantages such that it is possible to use various types of recording media such as Japanese paper, drawing paper, postcards, or plastic sheets, without pre-treatment.
On the other hand, U.S. Pat. Nos. 4,391,369 and 4,484,949 disclose ink which results in good printing quality irrespective of paper quality. Further, Japanese Patent Publication Open to Public Inspection No. 56-93776 discloses ultraviolet radiation curable resinous ink which results in desired adhesion onto metal surface. Still further, as an ink jet recording ink which is cured by exposure to ultraviolet radiation, for example, U.S. Pat. No. 4,228,438 discloses ink which is comprised of epoxy-modified acrylic resins and urethane-modified acrylic resins as a binder, as well as pigments comprised of particles of a diameter of at most 5 microns as a coloring component. Further, Japanese Patent Publication Open to Public Inspection No. 58-32674 discloses ink in which cationically polymerizable epoxy resins are employed as a binder, while Japanese Patent Publication Open to Public Inspection No. 5-186725 discloses ink comprised of water-soluble or water-insoluble dyes which can be easily printed on plain paper as well as recycled paper.
As noted above, demanded has been emergence of an ink jet recording method which is capable of carrying out highly detailed printing resulting in photographic quality images on various media such as plastic sheets without requiring ink special jet paper sheets.
However, when the aforesaid water-soluble liquid ink is employed, it becomes difficult to carry out printing on non-ink absorptive recording media. Even though special paper sheets are employed, a relatively large ink drying apparatus is required. In addition, it is difficult to carry out highly detailed printing due to problematic bleeding and resolution is limited, whereby its overall use is currently limited.
Even when hot-melt type ink using the aforesaid wax is employed, it is possible to carry out printing on non-absorptive recording media which exhibit no ink absorbability, and in addition to carry out high speed printing. However, the aforesaid hot-melt type ink causes problems in which the resulting images hardly exhibit sufficient reliability due to very low abrasion resistance and in addition, exhibit insufficient smoothness.
On the other hand, the ink jet recording systems, which employ organic pigments as a colorant, exhibit many advantages especially in the aspect of weather resistance, compared to ink jet recording systems employing dyes. As a result, being not limited to OA equipment, general home use printers, and office printers such as facsimile machines, the aforesaid ink jet recording system is expected to be (used for application of printing outdoor posters, large signboards, and decorations of cars, glass, elevators, walls, and buildings, as well as fabrics.
Further, an ink jet recording system employing an actinic radiation curable ink, which is cured by actinic radiation such as ultraviolet radiation, makes it possible to carry out printing on non-ink absorptive recording media. However in ink jet recording systems in which ink is not substantially comprised of water and organic solvents, and the liquid ink composition is cured by actinic radiation such as ultraviolet radiation, neither disclosure nor proposals are made which results in highly detailed printing under the control of dot diameter. Further, in highly detailed printing, it is essential that the formed dot diameter is controlled to be small and the contour is clear without bleeding. Further, when printing is carried out on non-ink absorptive media employing an ink jet recording system, it is difficult to control not only the amount of ink droplets but also the dot diameter. Particularly, it is a more difficult problem to control the diameter of dots formed by small droplets.
Further, when images are formed employing a plurality of kinds of ink in the same way as color printing, it is essential that in order to carry out highly detailed printing, dot shape formed by each kind of ink is uniform.
In order to control the aforesaid dot shape, it is effective to regulate the surface tension of the ink. For example, a method (refer to Patent Document 1) is proposed which specifies surface tension of ink to 25–35 mN/m. However, only specification of surface tension of ink, as described above, is insufficient to achieve highly detailed printing. Subsequently, technical improvement is further demanded.
(Patent Document 1)
International Patent Publication Open to Public Inspection No. WO 99/29788 (claims)